The giant leptocephalus (Coloconger giganteus) is a species of eel. It was first described by Peter Henry John Castle in 1959. It is a marine, deep-water dwelling eel which is distributed worldwide. It was thought that if it was indeed a leptocephalid, then it is probably the larvae of a Notacanthus species, most probably Notacanthus chemnitzii. However, in 2014, it was confirmed as a species of Coloconger.